delta.asm

   1 **
   2 ** Delta.asm
   3 **
   4 ** Copyright (C) 1995 Bernardo Innocenti
   5 **
   6 ** Delta encoding/decoding routine
   7 **
   8
   9 _DeltaDecode:
  10
  11 * void DeltaDecode (BYTE *dataBlock, ULONG blockSize);
  12 *                   A0                D0
  13 *
  14 *       old=0
  15 *       for i=0 to blockSize-1
  16 *               new=dataBlock[i]+old
  17 *               dataBlock[i]=new
  18 *               old=new
  19
  20         MOVEQ   #0,D1
  21
  22 $1
  23         ADD.B   (A0),D1
  24         MOVE.B  D1,(A0)+
  25
  26         SUBQ.L  #1,D0           ; Loop
  27         BNE             $1
  28
  29         RTS
  30
  31
  32 _DeltaEncode:
  33
  34 * void DeltaEncode (BYTE *dataBlock, ULONG blockSize);
  35 *                   A0                D0
  36 *
  37 *       old=0
  38 *       for i=0 to blockSize-1
  39 *               old=dataBlock[i]
  40 *               new=old-new
  41 *               datablock[i]=new
  42
  43
  44         MOVE.W  D2,-(SP)
  45         MOVEQ   #0,D1
  46
  47 $1
  48         MOVE.B  (A0),D2
  49         SUB.B   D2,D1
  50         MOVE.B  D1,(A0)+
  51
  52         SUBQ.L  #1,D0           ; Loop
  53         BNE             $1
  54
  55         MOVE.W  (SP)+,D2
  56         RTS